The present invention relates to a color filter substrate having a colored layer formed on a metal and to a manufacturing process therefor. More particularly, the present invention relates to a liquid crystal device using the above substrate and to a manufacturing process therefor, and relates to an electronic apparatus using the above device.
As is well known, liquid crystal devices do not themselves emit light; instead, they produce displays or the like simply by changing the paths of light. Therefore, all liquid crystal devices necessarily have some type of arrangement for directing light into panels. In view of this, liquid crystal devices are far different from other display devices, such as electroluminescent displays and plasma displays. A liquid crystal device in which light incident from a light source or the like disposed at a rear side of a panel is emitted to an observing side after passing through the panel is called a transmissive type, and a liquid crystal device in which ambient light incident from an observing side is emitted to an observing side by reflection by a panel, is called a reflective type.
In reflective type devices, the amount of ambient light incident from the observing side is not large compared to light incident from a light source disposed at a rear side of a panel. In addition, reflective type devices have high attenuation of light in each part thereof because, when the light is reflected, the light retraces its path through the panel, so that light emitted to an observing side is less than that in transmissive types. Accordingly, reflective type devices have a problem that display screens thereof are generally darker compared to transmissive type devices.
On the other hand, reflective type devices have advantages such as being able to produce a display not having a light source, which consumes large amount of electric power, being highly visible outdoors even in bright light, and the like. Hence, in some cases, the above advantages of reflective type devices overcome problems therein. Consequently, there is an increasing demand for reflective type liquid crystal devices for portable electronic apparatuses; however, a substantial problem remains in that when there is practically no ambient light, users cannot see the display of reflective type devices. A so-called xe2x80x9ctransflective liquid crystal devicexe2x80x9d is proposed as one solution to overcome this problem. In a bright environment, the liquid crystal device mainly uses reflection of ambient light, similar to that used in ordinary reflective type devices. However, in a dark environment, the transmissive type device is additionally used by lightning a light source disposed on a rear side of a panel, and therefore the device display can be seen in either situation. Moreover, concomitant with a recent demand for color displays for portable electronic devices, office automation apparatuses, and the like, color displays in transflective type liquid crystal devices are required in many cases.
A transflective liquid crystal device capable of providing a color display is described in, for example, Japan Unexamined Patent Application Publication No. 7-318919. The liquid crystal device which is disclosed in the above unexamined patent application, is provided inside a liquid crystal layer with pixel electrodes which also serve as a transflective film and has an arrangement for producing a color display. In the above arrangement, a color display is produced by coloring light by birefringent effects of a liquid crystal layer and a retardation film, and by polarization effects of polarizers provided at an observing side and at a rear side of a liquid crystal panel. Since the transflective film is provided inside the liquid crystal layer in the arrangement described above, double images, blurred display, and the like caused by parallax are avoided, and superior bright colored light can be obtained compared to an arrangement having a transflective film outside a liquid crystal layer.
However, the liquid crystal device described above has a problem of poor color reproducibility because light coloration is produced by birefringent effects and polarization effects.
The present invention was made taking the problem described above into consideration. A first object of the present invention is to provide a transflective or a reflective liquid crystal device with improved color reproducibility. As described in the above unexamined patent application, a transflective film is generally composed of aluminum or an aluminum alloy having aluminum as a primary component. When a colored layer, such as a color filter, a shading layer, or the like, is directly formed on the transflective film, aluminum is deteriorated during a forming process, and reflection characteristics may be seriously affected. When the colored layer is formed by an etching method, for example, a surface of the aluminum may be damaged by an etching solution. In addition, in some cases when the colored layer is formed by a color resist method, a surface of the aluminum may be damaged when the color resist is developed.
Accordingly, a second object of the present invention is to provide a color filter substrate, a liquid crystal device, and a manufacturing method therefor, in which, during a forming process for the colored layer, damage or deterioration of the aluminum, which is used as a metallic film for the transflective film and the reflective electrode, is prevented by a simple process.
To achieve the first object described above, the color filter substrate of the present invention, which is to be applied to the liquid crystal device, is a color filter substrate having a metallic film provided between the substrate and a colored layer, in which the metallic film and the colored layer are separated by a protective film provided between the metallic film and the colored layer.
According to the present invention, since the metallic film and the colored layer are separated by the protective film, the surface of the metallic film is not deteriorated when the colored layer is formed. Hence, a color filter substrate having good reflection characteristics at the metallic film is obtained.
An oxide film of the metallic film may be used as the protective film. In this case, an oxide film of the metallic film is preferably an anodized film. The reasons for this are that an anodizing method can easily control the thickness of the oxide film and form a dense oxide film having fewer defects such as pinholes. In addition, the colored layer may be formed by an electrodeposition method with proper thickness control.
As other examples of the protective films, oxides other than the metal oxide described above, organic dielectric films, and nitrides may be used. Oxides other than the metal oxide includes silicon oxides such as SiO2, the organic dielectric films include acrylic resins, and the nitrides include silicon nitrides, typically Si3N4. When an oxide other than the oxides of the metallic films is used as a protective film, reflectance deterioration can be suppressed because of a low refractive index. When an organic dielectric film is employed, a protective film can be easily formed by a method such as a spin coat method or a roll coat method. When a nitride is used as a protective film, an advantage is to suppress reflectance deterioration because of low refractive index.
The protective film may be formed by optionally combining two or more films among the above oxide films of the metal, an oxide films other than the above, the organic dielectric films, and the nitride films.
A metallic film including a primary component, such as aluminum, silver, chromium or the like, is used as the metallic film. When a metallic film including aluminum as a primary component is used, a metallic film having a high reflectance is obtained by using an inexpensive material. In addition, since an oxide film can be obtained from aluminum by anodization, a protective film composed of the oxide film can be easily formed. A preferable aluminum content in the metallic film is 85 weight percent or more. A metallic film having a very high reflectance is realized by a metallic film including silver as a primary component. A preferable silver content in the metallic film is 85 weight percent or more.
To achieve the first object described above, a method for manufacturing a color filter substrate of the present invention, which is to be applied to the liquid crystal device, is a method for manufacturing a color filter substrate having a metallic film provided between a substrate and a colored layer, comprising the steps of forming a protective film on the metallic film, and forming the colored layer on the protective film. In the method for manufacturing the color filter substrate, for the same reason as that in the color filter substrate described above, the surface of the metallic film is not deteriorated when the colored layer is formed. Hence, the color filter substrate having good reflection characteristics at the metallic film is realized. The step for forming the protective film includes a step for oxidizing the metallic film. Preferably, the metallic film is anodized. The reasons for this are that the anodizing method can easily control thickness of the oxide film and form a dense oxide film having fewer defects such as pinholes. In addition, the colored layer may be formed by an electrodeposition method with proper thickness control. Other matters not described here are similar to those described for the above color filter substrate.
The features of the liquid crystal device according to the present invention are that the liquid crystal device comprises a first substrate and a second substrate, a liquid crystal layer disposed between the first substrate and the second substrate, a metallic film disposed on the surface of the second substrate adjacent to the liquid crystal layer, which reflects incident light from the first substrate, and a colored layer provided above the surface of the metallic film adjacent to the liquid crystal layer, in which the metallic film and the colored layer are separated by a protective film provided therebetween. Since this liquid crystal device is provided with the color filter substrate, the surface of the metallic film is not deteriorated when the colored layer is formed. Hence, reflection characteristics are improved.
In the embodiment of this liquid crystal device, the protective film includes an oxide film of the metallic film. In this case, the oxide film of the metallic film is preferably an anodized film. According to this embodiment, an anodizing method can easily control the thickness of the oxide film and can form a dense oxide film having fewer defects such as pinholes.
Next, the features of the method for manufacturing the liquid crystal device according to the present invention will be described. The liquid crystal device comprises a first substrate and a second substrate, a liquid crystal layer disposed between the first and the second substrate, a metallic film formed on the surface of the second substrate adjacent to the liquid crystal layer, which reflects incident light from the first substrate, and a colored layer provided above the surface of the metallic film adjacent to the liquid crystal layer. The method for manufacturing the liquid crystal device comprises the steps of forming a protective film on the metallic film, and forming the colored layer on the protective film. Since this manufacturing method includes the method for manufacturing the color filter substrate described above, the surface of the metallic film is not deteriorated when the colored layer is formed. Hence, reflection characteristics are improved.
In the embodiment of this manufacturing method, the steps for forming the protective film includes a step for oxidizing the metallic film. Preferably, the metallic film is anodized. The reasons for this are that the anodizing method can easily control the thickness of the oxide film and can form a dense oxide film having fewer defects such as pinholes. In addition, the colored layer may be formed by an electrodeposition method with proper thickness control. Other matters not described here are similar to those described in the above color filter substrate and the manufacturing method therefor.
Features of an electronic apparatus according to the present invention will be described. The electronic apparatus is provided with a crystal liquid device as a display portion which comprises a first substrate and a second substrate, a liquid crystal layer disposed between the first and the second substrate, a metallic film formed on the surface of the second substrate adjacent to the liquid crystal layer, which reflects incident light from the first substrate, and a colored layer provided above the surface of the metallic film adjacent to the liquid crystal layer, in which the metallic film and the colored layer are separated by a protective film provided therebetween. Since this electronic apparatus is provided with the liquid crystal device described above, an electronic apparatus having superior image display can be realized.
A specific liquid crystal device according to the present invention, which achieves the first object and the second object, will be explained. First, to achieve the first object, a first liquid crystal device of the present invention comprises a first transparent substrate and a second transparent substrate, a liquid crystal layer disposed between the first substrate and the second substrate, a transparent electrode formed on the surface of the first substrate adjacent to the liquid crystal layer, a transflective electrode formed on the surface of the second substrate adjacent to the liquid crystal layer, and the colored layer formed on the upper surface of the transflective electrode.
According to the first liquid crystal device, in the transmissive display, incident light from the second substrate passes through the colored layer and the liquid crystal layer sequentially after being transmitted through the transflective electrode, and is then emitted at the first substrate side. Whereas, in the reflective display, incident light from the first substrate is reflected at the transflective electrode after passing through the liquid crystal layer and the colored layer sequentially, and is then emitted at the first substrate side after retracing its path through which the light passed. Consequently, in both the transmissive display and the reflective display, light is transmitted through the colored layer, so that the first object of improving color reproducibility can be achieved. In addition, the distance from the transflective electrode to the liquid crystal layer is short, since the transflective electrode is formed on the surface of the second substrate adjacent to the liquid crystal layer. Hence, in the reflective display, generation of double images and blurred display caused by parallax can be avoided.
In the liquid crystal device described above, a lighting unit such as a backlight may be provided at the second substrate at the side thereof opposite to the liquid crystal layer. When the lighting unit described above is provided, light from the lighting unit is transmitted through the transflective electrode, so that a bright display can be obtained in a dark environment by additionally functioning as a transmissive display.
When a metal, such as aluminum, silver, or chromium, is formed to have a thickness of approximately 15 to 20 nm and is used as the transflective electrode, a transflective film is obtained having a reflectance of approximately 85% and a transmittance of approximately 10%. When a metal having aluminum as a primary component is specifically used, inexpensive, high reflectance transflective electrode can be realized. When a metal having aluminum as a primary component is used, a preferable content thereof is 85% or more.
In the embodiment of the first liquid crystal device, a protective film is formed between the colored layer and the transflective electrode. According to this embodiment, since the colored layer and the transflective electrode are separated by the protective film, the second object of beforehand preventing damage and deterioration of aluminum used as the transflective electrode can be achieved by a simple process.
The protective film is preferably an anodized film of the metal constituting the transflective electrode. The reasons for that are that the anodizing method can easily control the thickness of the oxide film and can form a dense oxide film having fewer defects such as pinholes. In addition, the colored layer may be formed by a so-called xe2x80x9celectrodeposition methodxe2x80x9d with proper thickness control.
As other examples of the protective films, oxide films other than the metal constituting the transflective electrode, nitride films, and organic dielectric films, may be used. The oxide films include silicon oxides such as SiO2, and nitride films include silicon nitrides, typically Si3N4, both of which can be formed by chemical vapor deposition. The organic dielectric films include acrylic resins, which can be formed by a spin coat method or a roll coat method. Furthermore, the protective film may be formed by optionally combining two or more films among the oxide films of the metal constituting the transflective electrode, the oxide films other than above, the organic dielectric films, and the nitride films. Thus, the thickness of the protective film is reduced, so that deterioration of reflectance can be suppressed as much as possible.
In another embodiment of the first liquid crystal device, the transflective electrode is provided with an opening in the form of a slit, and the colored layer is formed in an area corresponding to that at which the slit is formed. According to this embodiment, in the transmissive display, light is transmitted through (passes through) a slit as well as passes through the colored layer and the liquid crystal layer sequentially, and is emitted at the first substrate side. Since the colored layer is formed in an area corresponding to that at which the slit is provided, light passing through the slit is colored by the colored layer, so that color reproducibility of the transmissive display can be improved.
Various driving methods for the first liquid crystal device may be employed, which include a passive matrix method and other methods such as an active matrix method. Among these, when the active matrix method is employed, the following embodiment may be considered. That is, in one embodiment employing the active matrix method for the first liquid crystal device, the transflective electrode also serves as a pixel electrode, and a switching element is connected to each pixel electrode described above. In this embodiment, since the transflective electrode also serves as a pixel electrode, and a switching element is connected to each pixel electrode, an ON pixel and an OFF pixel can be separated electrically by the switching element. Therefore, a liquid crystal device having superior contrast and response, and very fine display, can be easily achieved.
In another embodiment employing the active matrix method for the first liquid crystal device, the transparent electrode also serves as a pixel electrode, and a switching element is connected to each pixel electrode described above. According to this embodiment, since the transparent electrode also serves as a pixel electrode, and a switching element is connected to each pixel electrode, an ON pixel and an OFF pixel can be separated electrically by the switching element. Therefore, a liquid crystal device having superior contrast and response, and very fine display, can be easily achieved.
Various elements such as a thin film diode (TFD) and a thin film transistor (TFT) can be used as a switching element in these embodiments.
The first object can also be achieved by a first electronic apparatus provided with the first liquid crystal device described above. According to the first electronic apparatus, in both the transmissive display and the reflective display, various electronic apparatuses can be produced provided with the liquid crystal devices which have improved color reproducibility and no generation of double images and blurred display caused by parallax. Consequently, the electronic apparatus as described above can produce high quality display in a bright and a dark environment, regardless of the level of ambient light.
To achieve the first object described above, the second liquid crystal device of the invention comprises a first transparent substrate and a second transparent substrate, a liquid crystal layer disposed between the first and the second substrate, a first transparent electrode formed on the surface of the first substrate adjacent to the liquid crystal layer, a transflective film formed on the surface of the second substrate adjacent to the liquid crystal layer, a colored layer formed on the upper surface of the transflective electrode, and a second transparent electrode formed on the upper surface of the colored layer.
According to the second liquid crystal device, in the transmissive display, incident light from the second substrate passes through the colored layer, the second transparent electrode, and the liquid crystal layer sequentially after being transmitted through the transflective electrode, and is then emitted at the first substrate side. Whereas, in the reflective display, incident light from the first substrate is reflected at the transflective electrode after passing through the liquid crystal layer, the second transparent electrode, and the colored layer sequentially, and is then emitted at the first substrate side after retracing its path through which the light passed. Consequently, in both the transmissive display and the reflective display, light is transmitted through the colored layer, so that the improvement of color reproducibility can be achieved. Similar to the first liquid crystal device, the first object described above can be achieved. In addition, the distance from the transflective electrode to the liquid crystal layer is short, since the transflective electrode is formed on the surface of the second substrate adjacent to the liquid crystal layer. Hence, in the reflective display, generation of double images and blurred display caused by parallax can also be avoided.
In the second liquid crystal device, similar to that in the first liquid crystal device described above, a lighting unit may be provided at the second substrate at the side thereof opposite to the liquid crystal layer. When the lighting unit described above is provided, light from the lighting unit is transmitted through the transflective electrode, so that a bright display can be obtained in a dark environment by additionally functioning as a transmissive display.
In the embodiment of the second liquid crystal device, a protective film is formed between the colored layer and the transflective electrode. In this embodiment, since the colored layer and the transflective electrode are separated by the protective film, the second object of preventing damage and deterioration of aluminum used as the transflective electrode can be achieved by a simple process.
The protective film is preferably an anodized film of the metal constituting the transflective film. The reasons for that are that the thickness of the anodized film can be easily controlled, and the film can be formed as a dense film having fewer defects such as pinholes. In addition, the colored layer may be formed by a so-called xe2x80x9celectrodeposition methodxe2x80x9d with proper thickness control. As other examples of the protective films, oxide films other than the metal constituting the transflective film, nitride films, and organic dielectric films may be used, and two or more films described above may be optionally combined.
In another embodiment of the second liquid crystal device, the transflective electrode is provided with an opening in the form of a slit, and the colored layer is formed in an area corresponding to that at which the slit is formed. According to this embodiment, in the transmissive display, light is transmitted through (passes through) a slit as well as passes through the colored layer, the second transparent electrode, and the liquid crystal layer sequentially, and is emitted at the first substrate side. Since the colored layer is formed in an area corresponding to that at which the slit is provided, light passing through the slit is colored by the colored layer, so that color reproducibility of the transmissive display can be improved.
Compared to the first liquid crystal device described above having a slit at the transflective electrode, the second transparent electrode is present in the opening of the slit, so that an electric field is applied to the opening of the slit. Hence, liquid crystal molecules positioned at the slit portion are oriented regardless of the electric field leakage from the edge of the slit; light having no rotary polarization is prevented from passing through the slit. As a result, display quality is improved. Moreover, the slit can be formed independently from a forming area for a pixel or a dot.
Similar to the first liquid crystal device, various driving methods for the second liquid crystal device may be employed, which include a passive matrix method and other methods such as an active matrix method. Among these, in an embodiment to which the active matrix method is applied, the second transparent electrode also serves as a pixel electrode, and a switching element is connected to each pixel electrode described above. In this embodiment, since the second transparent electrode also serves as a pixel electrode, and a switching element is connected to each pixel electrode, an ON pixel and an OFF pixel can be separated electrically by the switching element. Therefore, a liquid crystal device having superior contrast and response, and very fine display, can be easily achieved.
In another embodiment employing the active matrix method for the second liquid crystal device, the first transparent electrode also serves as a pixel electrode, and a switching element is connected to each pixel electrode described above. According to this embodiment, since the first transparent electrode also serves as a pixel electrode, and a switching element is connected to each pixel electrode, similar to the above, an ON pixel and an OFF pixel can be separated electrically by the switching element. Therefore, a liquid crystal device having superior contrast and response, and very fine display, can be easily achieved. In addition, the switching element is provided at the first substrate side in which the first transparent electrode is formed, instead of at the second substrate side in which the colored layer is formed on the lower layer of the second transparent electrode, so that no consideration of heat stability of the colored layer in the process for manufacturing the switching element is necessary. Therefore, flexibility in the manufacturing process can be enhanced. Similar to the first liquid crystal device, various elements such as a thin film diode (TFD) and a thin film transistor (TFT) can also be used as a switching element in these embodiments.
The first object described above can also be achieved by a second electronic apparatus provided with the second liquid crystal device described above. According to the second electronic apparatus, in both the transmissive display and the reflective display, various electronic apparatuses can be produced provided with the liquid crystal devices which have improved color reproducibility and no generation of double images and blurred display caused by parallax. Consequently, the electronic apparatus as described above can yield high quality display in a bright environment and a dark environment, regardless of the level of ambient light.
For simultaneously achieving the first and the second objects described above, the third liquid crystal device of the present invention comprises a first substrate and a second substrate, a liquid crystal layer disposed between the first substrate and the second substrate, a transparent electrode formed on the surface of the first substrate adjacent to the liquid crystal layer, a reflective electrode formed on the surface of the second substrate adjacent to the liquid crystal layer, a protective film for protecting the reflective electrode, and a colored layer formed on the upper surface of the protective film.
According to the third liquid crystal device, incident light from the first substrate side is reflected at the reflective electrode after passing through the liquid crystal layer, the colored layer, and the protective film sequentially, and is then emitted at the first substrate side after retracing its path through which the light passed. At this step, since the light is colored by the colored layer formed above the upper surface of the reflective electrode with the protective film therebetween, the first object described above of improving color reproducibility can be achieved. At the same time, since the colored layer and the reflective electrode are separated by the protective film formed therebetween, damage or deterioration of aluminum used as the reflective electrode during the process for forming the colored layer is prevented beforehand by a simple process, whereby the second object can be achieved. In addition, since the reflective electrode is formed on the liquid crystal layer side of the second substrate, the distance from the reflective electrode to the liquid crystal layer is short. Hence, generation of double images and blurred display caused by parallax can be avoided.
The protective film is preferably an anodized film of the metal constituting the reflective electrode. The reasons for this are that the thickness of the anodized film can be easily controlled, and the film can be formed as a dense film having fewer defects such as pinholes. In addition, the colored layer may be formed by a so-called xe2x80x9celectrodeposition methodxe2x80x9d with proper thickness control. As other examples of the protective films, oxide films other than the metal constituting the transflective films, nitride films, and organic dielectric films may be used, and two or more films described above may be optionally combined.
As a driving method for the third liquid crystal device, similar to the first and the second liquid crystal devices, various driving methods may be employed, which include a passive matrix method and other methods such as an active matrix method. Among those, in an embodiment to which the active matrix method is applied, the reflective electrode also serves as a pixel electrode, and a switching element is connected to each pixel electrode described above. In this embodiment, since the reflective electrode also serves as a pixel electrode, and a switching element is connected to each pixel electrode, an ON pixel and an OFF pixel can be separated electrically by the switching element. Therefore, a liquid crystal device having superior contrast and response, and very fine display, can be easily achieved.
In another embodiment employing the active matrix method for the third liquid crystal device, the transparent electrode described above also serves as a pixel electrode, and a switching element is connected to each pixel electrode described above. According to this embodiment, since the transparent electrode also serves as a pixel electrode, and a switching element is connected to each pixel electrode, an ON pixel and an OFF pixel can be separated electrically by the switching element. Therefore, a liquid crystal device having superior contrast and response, and very fine display, can be easily achieved. Similar to the first and the second liquid crystal devices, various elements such as a TFT element and a TFD element can be used as a switching element in these embodiments.
The first and the second objects can also be achieved by a third electronic apparatus having the third liquid crystal device described above. According to the third electronic apparatus in the reflective display, various electronic apparatuses can be produced provided with the liquid crystal devices which have improved color reproducibility and no generation of double images and blurred display caused by parallax.